It has previously been proposed--see German patent disclosure document DE-OS No. 28 09 712, to utilize threshold switches which respond when certain operating parameters within the electrical network are passed. For example, stoppage of the generator can be indicated since the voltage of a generator will rapidly drop. Thus, an indication, for example, of belt-breakage of the belt drive of the generator in an automotive vehicle will be shown another threshhold switch is provided to indicate malfunction of the voltage regulator, for example if the control switch, typically a transistor, within the voltage regulator should alloy-through so that the output voltage of the generator will rise to an excessive level. Another threshhold stage can be provided which results in an indication if the command voltage for the generator should drop below a predetermined value, so that the main power switch of the regulator is erroneously blocked.
The signal inputs to the threshhold stages are connected, in dependence on their function, to a predetermined junction point on the generator, to which cathodes of sensing diodes are connected as well as the terminal of the main switch, for example the ignition switch, which is remote from the battery junction.
The system is adequately suited to determine malfunction within the generator and the control system therefor. In some systems, however, it is also desirable to provide malfunction indication for faults in the electrical network, and associated elements, which are outside of the on-board network directly associated with the generator. It is, for example, desirable in some installations to also provide a monitoring arrangement which can determine the charge-state of the battery and to obtain a battery sensing signal if connected loads should exceed the power supply capabilities of the alternator so that, in due course, the battery would discharge.